Even if you take the lead and die 10 seconds later, there was still 30 seconds on the clock.

I disagree.

The game ends when everyone is corrupted or when the time runs out. Both the end of the clock and the last person being corrupted are the end of the game. The last 10 sec before that happens are the last 10 seconds of the game.

This challenge is glitched. You can actually get and immediately lose the lead in last 10s and still get credit. So it's purely clock-based. You see red countdown + hear "you have taken a lead" = you given a progress on that challenge.

That is a change from brotherhood when the challenge required taking the lead and winning the game. This one specifically just requires taking the lead in that last 10 seconds of clock time. What would be fun to see is if it will count it when you do it twice in a game.

Thats where the confusion is Kytr. The description of the challenge should be worded so that it says "Take the lead in the last 10 seconds of the clock timer for the session," or something like that.

Based on how the challenge functions incorruption, that phrasing would have been better. I think that was not done because they did not consider that corruption games almost always end before the clock runs out on the last round. My prior post was mainly directed at the concept that taking and losing the lead in the last 10 seconds and getting credit demonstrated that the challenge was glitched, since winning the game was not part of the challenge.

The reality is that it would be difficult to work this challenge into corruption, since there is no way to know when most games will end until they do end -- about 10 seconds after the usurper checks should have been started.

Timestamp when a player takes the lead, and compare it to the time when the match ends. If it's less than 10 seconds, they complete the challenge. The game would only need to track a single 3-digit timestamp, changing which timestamp it's using every time a new player takes the lead.

That will not quite do it. It is possible to take the lead more than once in the final 10 seconds. It is unlikely to happen (especially in corruption), especially in this mode, but could still happen. If the system where to maintain the list of all lead changes for the last 10 second, it would be possible to reconstruct who had made the usurper challenge based on that information.